Bruce Katz, founding director of the metropolitan policy programme at the influential Brookings Institution thinktank, spoke to Guardian Local Leaders about his new book, the power of cities and city leaders in reshaping the economy – and how US country singer Dolly Parton can help.

What do you think of the UK relationship between central and local government?

The UK is highly centralised and, because of this, it is missing an opportunity. The core cities in the north, such as Manchester and Birmingham, as well as places like Bristol could be competitive middleweights in the world. Obviously, London exists on its own, but these other cities can thrive and prosper if they understand their particular niche.

There is a famous Dolly Parton quote: "Find out who you are and do it on purpose." Obviously, she didn't intend this advice to apply to cities but it does. Places like Manchester, for example, need to work out what their unique offering is compared to Sheffield and Newcastle. These are really different economies when you think about it.

Are there any good examples of this from the US?

Portland, Oregon is a great example. In the US, Portland is derided as being weird and a magnet for hippies and people who have alternative lifestyles. But it is also an export powerhouse. In the past 40 years Portland has built a strong base of environmental farms that provide sustainable products and services for places in Asia and Latin America.

Portland was hit hard by the recession, but the city understood it had a unique export profile and has established a new export strategy, labelled "we build green cities". Portland is selling corporations to Chinese and Indian cities under a unified brand as being the companies that can really help these cities grow in a way where [citizens] can breathe the air and drink the water.

Which UK cities particularly impress you?

Manchester is a very distinctive city, and the way it has come together as a combined authority working with business and universities is impressive.

In your book you talk about a "next economy". What do you mean by this?

The pre-recession economy was characterised by debt, housebuilding, financialisation and consumption. As we come out of the recession, there is a view that we need to shift to an economy that gets back to basics, fuelled by innovation and not just idea generation but technology-driven production. You need an economy driven by advanced energy sources with lower carbon emissions; you need an economy that is driven by exports and foreign investment.

How important is HS2 for the UK?

In some respects some of these northern cities are suburbs of London. This could be an American perspective in the sense that we do not think about the time it takes travelling to do business or commuting. Really, you are talking about very short distances between these places in the UK. If you built a system like high-speed rail then it would probably help distribute your economy in a more balanced way.

Do you think city mayors like Boris Johnson should have greater powers?

In many ways Boris is the chief marketer of London and he is very good at that, but he should have more power. The American message would be to ask why central government should do so much when it should be focusing on the job of a national government and not mucking around interfering in what cities are better at, and locally grounded issues. Too much revenue in this country is raised nationally, and when you do that you never reward places for doing smart things.

Can cities grow without damaging the environment?

Portland and Copenhagen are cities that have done this. They are not very big, but they are prosperous cities committed to growth. They have followed the pattern of sprawl less and have invested more.